Stand-by distributed storage units

ABSTRACT

A method for execution by a dispersed storage network (DSN), the method begins by determining a failure rate of storage units of an active storage unit pool, establishing a number of standby storage units based on the determined failure rate, identifying an associated DSN address range of the failed storage unit, selecting an available standby storage unit, facilitating populating the selected available standby storage unit with data slices associated with the failed storage unit, utilizing the selected available standby storage unit, facilitating population of a replacement storage unit with the data slices from the selected available standby storage unit and facilitating processing of further receive data access requests for data associated with the associated DSN address range by utilizing the replacement storage unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present U.S. Utility patent application claims priority pursuant to35 U.S.C. § 120, as a continuation-in-part (CIP) of U.S. Utilityapplication Ser. No. 14/986,279, entitled “STORING DATA IN A DISPERSEDSTORAGE NETWORK,” filed Dec. 31, 2015, which claims priority pursuant to35 U.S.C. § 119(e) to U.S. Provisional Application No. 62/121,667,entitled “SELECTING A STORAGE POOL OF A DISPERSED STORAGE NETWORK,”filed Feb. 27, 2015, all of which are hereby incorporated herein byreference in their entirety and made part of the present U.S. Utilitypatent application for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION Technical Field of the Invention

This invention relates generally to computer networks and moreparticularly to dispersing error encoded data.

Description of Related Art

Computing devices are known to communicate data, process data, and/orstore data. Such computing devices range from wireless smart phones,laptops, tablets, personal computers (PC), work stations, and video gamedevices, to data centers that support millions of web searches, stocktrades, or on-line purchases every day. In general, a computing deviceincludes a central processing unit (CPU), a memory system, userinput/output interfaces, peripheral device interfaces, and aninterconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using“cloud computing” to perform one or more computing functions (e.g., aservice, an application, an algorithm, an arithmetic logic function,etc.) on behalf of the computer. Further, for large services,applications, and/or functions, cloud computing may be performed bymultiple cloud computing resources in a distributed manner to improvethe response time for completion of the service, application, and/orfunction. For example, Hadoop is an open source software framework thatsupports distributed applications enabling application execution bythousands of computers.

In addition to cloud computing, a computer may use “cloud storage” aspart of its memory system. As is known, cloud storage enables a user,via its computer, to store files, applications, etc. on an Internetstorage system. The Internet storage system may include a RAID(redundant array of independent disks) system and/or a dispersed storagesystem that uses an error correction scheme to encode data for storage.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a dispersed ordistributed storage network (DSN) in accordance with the presentinvention;

FIG. 2 is a schematic block diagram of an embodiment of a computing corein accordance with the present invention;

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data in accordance with the present invention;

FIG. 4 is a schematic block diagram of a generic example of an errorencoding function in accordance with the present invention;

FIG. 5 is a schematic block diagram of a specific example of an errorencoding function in accordance with the present invention;

FIG. 6 is a schematic block diagram of an example of a slice name of anencoded data slice (EDS) in accordance with the present invention;

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of data in accordance with the present invention;

FIG. 8 is a schematic block diagram of a generic example of an errordecoding function in accordance with the present invention;

FIG. 9 is a schematic block diagram of another embodiment of a dispersedstorage network (DSN) in accordance with the present invention; and

FIG. 9A is a flowchart illustrating an example of utilizing storageresources in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a dispersed, ordistributed, storage network (DSN) 10 that includes a plurality ofcomputing devices 12-16, a managing unit 18, an integrity processingunit 20, and a DSN memory 22. The components of the DSN 10 are coupledto a network 24, which may include one or more wireless and/or wirelined communication systems; one or more non-public intranet systemsand/or public internet systems; and/or one or more local area networks(LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of storage units 36 that may belocated at geographically different sites (e.g., one in Chicago, one inMilwaukee, etc.), at a common site, or a combination thereof. Forexample, if the DSN memory 22 includes eight storage units 36, eachstorage unit is located at a different site. As another example, if theDSN memory 22 includes eight storage units 36, all eight storage unitsare located at the same site. As yet another example, if the DSN memory22 includes eight storage units 36, a first pair of storage units are ata first common site, a second pair of storage units are at a secondcommon site, a third pair of storage units are at a third common site,and a fourth pair of storage units are at a fourth common site. Notethat a DSN memory 22 may include more or less than eight storage units36. Further note that each storage unit 36 includes a computing core (asshown in FIG. 2, or components thereof) and a plurality of memorydevices for storing dispersed error encoded data.

Each of the computing devices 12-16, the managing unit 18, and theintegrity processing unit 20 include a computing core 26, which includesnetwork interfaces 30-33. Computing devices 12-16 may each be a portablecomputing device and/or a fixed computing device. A portable computingdevice may be a social networking device, a gaming device, a cell phone,a smart phone, a digital assistant, a digital music player, a digitalvideo player, a laptop computer, a handheld computer, a tablet, a videogame controller, and/or any other portable device that includes acomputing core. A fixed computing device may be a computer (PC), acomputer server, a cable set-top box, a satellite receiver, a televisionset, a printer, a fax machine, home entertainment equipment, a videogame console, and/or any type of home or office computing equipment.Note that each of the managing unit 18 and the integrity processing unit20 may be separate computing devices, may be a common computing device,and/or may be integrated into one or more of the computing devices 12-16and/or into one or more of the storage units 36.

Each interface 30, 32, and 33 includes software and hardware to supportone or more communication links via the network 24 indirectly and/ordirectly. For example, interface 30 supports a communication link (e.g.,wired, wireless, direct, via a LAN, via the network 24, etc.) betweencomputing devices 14 and 16. As another example, interface 32 supportscommunication links (e.g., a wired connection, a wireless connection, aLAN connection, and/or any other type of connection to/from the network24) between computing devices 12 & 16 and the DSN memory 22. As yetanother example, interface 33 supports a communication link for each ofthe managing unit 18 and the integrity processing unit 20 to the network24.

Computing devices 12 and 16 include a dispersed storage (DS) clientmodule 34, which enables the computing device to dispersed storage errorencode and decode data as subsequently described with reference to oneor more of FIGS. 3-9A. In this example embodiment, computing device 16functions as a dispersed storage processing agent for computing device14. In this role, computing device 16 dispersed storage error encodesand decodes data on behalf of computing device 14. With the use ofdispersed storage error encoding and decoding, the DSN 10 is tolerant ofa significant number of storage unit failures (the number of failures isbased on parameters of the dispersed storage error encoding function)without loss of data and without the need for a redundant or backupcopies of the data. Further, the DSN 10 stores data for an indefiniteperiod of time without data loss and in a secure manner (e.g., thesystem is very resistant to unauthorized attempts at accessing thedata).

In operation, the managing unit 18 performs DS management services. Forexample, the managing unit 18 establishes distributed data storageparameters (e.g., vault creation, distributed storage parameters,security parameters, billing information, user profile information,etc.) for computing devices 12-14 individually or as part of a group ofuser devices. As a specific example, the managing unit 18 coordinatescreation of a vault (e.g., a virtual memory block associated with aportion of an overall namespace of the DSN) within the DSTN memory 22for a user device, a group of devices, or for public access andestablishes per vault dispersed storage (DS) error encoding parametersfor a vault. The managing unit 18 facilitates storage of DS errorencoding parameters for each vault by updating registry information ofthe DSN 10, where the registry information may be stored in the DSNmemory 22, a computing device 12-16, the managing unit 18, and/or theintegrity processing unit 20.

The DSN managing unit 18 creates and stores user profile information(e.g., an access control list (ACL)) in local memory and/or withinmemory of the DSN memory 22. The user profile information includesauthentication information, permissions, and/or the security parameters.The security parameters may include encryption/decryption scheme, one ormore encryption keys, key generation scheme, and/or dataencoding/decoding scheme.

The DSN managing unit 18 creates billing information for a particularuser, a user group, a vault access, public vault access, etc. Forinstance, the DSTN managing unit 18 tracks the number of times a useraccesses a non-public vault and/or public vaults, which can be used togenerate per-access billing information. In another instance, the DSTNmanaging unit 18 tracks the amount of data stored and/or retrieved by auser device and/or a user group, which can be used to generateper-data-amount billing information.

As another example, the managing unit 18 performs network operations,network administration, and/or network maintenance. Network operationsincludes authenticating user data allocation requests (e.g., read and/orwrite requests), managing creation of vaults, establishingauthentication credentials for user devices, adding/deleting components(e.g., user devices, storage units, and/or computing devices with a DSclient module 34) to/from the DSN 10, and/or establishing authenticationcredentials for the storage units 36. Network administration includesmonitoring devices and/or units for failures, maintaining vaultinformation, determining device and/or unit activation status,determining device and/or unit loading, and/or determining any othersystem level operation that affects the performance level of the DSN 10.Network maintenance includes facilitating replacing, upgrading,repairing, and/or expanding a device and/or unit of the DSN 10.

The integrity processing unit 20 performs rebuilding of ‘bad’ or missingencoded data slices. At a high level, the integrity processing unit 20performs rebuilding by periodically attempting to retrieve/list encodeddata slices, and/or slice names of the encoded data slices, from the DSNmemory 22. For retrieved encoded slices, they are checked for errors dueto data corruption, outdated version, etc. If a slice includes an error,it is flagged as a ‘bad’ slice. For encoded data slices that were notreceived and/or not listed, they are flagged as missing slices. Badand/or missing slices are subsequently rebuilt using other retrievedencoded data slices that are deemed to be good slices to produce rebuiltslices. The rebuilt slices are stored in the DSTN memory 22.

FIG. 2 is a schematic block diagram of an embodiment of a computing core26 that includes a processing module 50, a memory controller 52, mainmemory 54, a video graphics processing unit 55, an input/output (TO)controller 56, a peripheral component interconnect (PCI) interface 58,an IO interface module 60, at least one IO device interface module 62, aread only memory (ROM) basic input output system (BIOS) 64, and one ormore memory interface modules. The one or more memory interfacemodule(s) includes one or more of a universal serial bus (USB) interfacemodule 66, a host bus adapter (HBA) interface module 68, a networkinterface module 70, a flash interface module 72, a hard drive interfacemodule 74, and a DSN interface module 76.

The DSN interface module 76 functions to mimic a conventional operatingsystem (OS) file system interface (e.g., network file system (NFS),flash file system (FFS), disk file system (DFS), file transfer protocol(FTP), web-based distributed authoring and versioning (WebDAV), etc.)and/or a block memory interface (e.g., small computer system interface(SCSI), internet small computer system interface (iSCSI), etc.). The DSNinterface module 76 and/or the network interface module 70 may functionas one or more of the interface 30-33 of FIG. 1. Note that the IO deviceinterface module 62 and/or the memory interface modules 66-76 may becollectively or individually referred to as IO ports.

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data. When a computing device 12 or 16 has data tostore it disperse storage error encodes the data in accordance with adispersed storage error encoding process based on dispersed storageerror encoding parameters. The dispersed storage error encodingparameters include an encoding function (e.g., information dispersalalgorithm, Reed-Solomon, Cauchy Reed-Solomon, systematic encoding,non-systematic encoding, on-line codes, etc.), a data segmentingprotocol (e.g., data segment size, fixed, variable, etc.), and per datasegment encoding values. The per data segment encoding values include atotal, or pillar width, number (T) of encoded data slices per encodingof a data segment i.e., in a set of encoded data slices); a decodethreshold number (D) of encoded data slices of a set of encoded dataslices that are needed to recover the data segment; a read thresholdnumber (R) of encoded data slices to indicate a number of encoded dataslices per set to be read from storage for decoding of the data segment;and/or a write threshold number (W) to indicate a number of encoded dataslices per set that must be accurately stored before the encoded datasegment is deemed to have been properly stored. The dispersed storageerror encoding parameters may further include slicing information (e.g.,the number of encoded data slices that will be created for each datasegment) and/or slice security information (e.g., per encoded data sliceencryption, compression, integrity checksum, etc.).

In the present example, Cauchy Reed-Solomon has been selected as theencoding function (a generic example is shown in FIG. 4 and a specificexample is shown in FIG. 5); the data segmenting protocol is to dividethe data object into fixed sized data segments; and the per data segmentencoding values include: a pillar width of 5, a decode threshold of 3, aread threshold of 4, and a write threshold of 4. In accordance with thedata segmenting protocol, the computing device 12 or 16 divides the data(e.g., a file (e.g., text, video, audio, etc.), a data object, or otherdata arrangement) into a plurality of fixed sized data segments (e.g., 1through Y of a fixed size in range of Kilo-bytes to Tera-bytes or more).The number of data segments created is dependent of the size of the dataand the data segmenting protocol.

The computing device 12 or 16 then disperse storage error encodes a datasegment using the selected encoding function (e.g., Cauchy Reed-Solomon)to produce a set of encoded data slices. FIG. 4 illustrates a genericCauchy Reed-Solomon encoding function, which includes an encoding matrix(EM), a data matrix (DM), and a coded matrix (CM). The size of theencoding matrix (EM) is dependent on the pillar width number (T) and thedecode threshold number (D) of selected per data segment encodingvalues. To produce the data matrix (DM), the data segment is dividedinto a plurality of data blocks and the data blocks are arranged into Dnumber of rows with Z data blocks per row. Note that Z is a function ofthe number of data blocks created from the data segment and the decodethreshold number (D). The coded matrix is produced by matrix multiplyingthe data matrix by the encoding matrix.

FIG. 5 illustrates a specific example of Cauchy Reed-Solomon encodingwith a pillar number (T) of five and decode threshold number of three.In this example, a first data segment is divided into twelve data blocks(D1-D12). The coded matrix includes five rows of coded data blocks,where the first row of X11-X14 corresponds to a first encoded data slice(EDS 1_1), the second row of X21-X24 corresponds to a second encodeddata slice (EDS 2_1), the third row of X31-X34 corresponds to a thirdencoded data slice (EDS 3_1), the fourth row of X41-X44 corresponds to afourth encoded data slice (EDS 4_1), and the fifth row of X51-X54corresponds to a fifth encoded data slice (EDS 5_1). Note that thesecond number of the EDS designation corresponds to the data segmentnumber.

Returning to the discussion of FIG. 3, the computing device also createsa slice name (SN) for each encoded data slice (EDS) in the set ofencoded data slices. A typical format for a slice name 60 is shown inFIG. 6. As shown, the slice name (SN) 60 includes a pillar number of theencoded data slice (e.g., one of 1-T), a data segment number (e.g., oneof 1-Y), a vault identifier (ID), a data object identifier (ID), and mayfurther include revision level information of the encoded data slices.The slice name functions as, at least part of, a DSN address for theencoded data slice for storage and retrieval from the DSN memory 22.

As a result of encoding, the computing device 12 or 16 produces aplurality of sets of encoded data slices, which are provided with theirrespective slice names to the storage units for storage. As shown, thefirst set of encoded data slices includes EDS 1_1 through EDS 5_1 andthe first set of slice names includes SN 1_1 through SN 5_1 and the lastset of encoded data slices includes EDS 1_Y through EDS 5_Y and the lastset of slice names includes SN 1_Y through SN 5_Y.

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of a data object that was dispersed storage error encodedand stored in the example of FIG. 4. In this example, the computingdevice 12 or 16 retrieves from the storage units at least the decodethreshold number of encoded data slices per data segment. As a specificexample, the computing device retrieves a read threshold number ofencoded data slices.

To recover a data segment from a decode threshold number of encoded dataslices, the computing device uses a decoding function as shown in FIG.8. As shown, the decoding function is essentially an inverse of theencoding function of FIG. 4. The coded matrix includes a decodethreshold number of rows (e.g., three in this example) and the decodingmatrix in an inversion of the encoding matrix that includes thecorresponding rows of the coded matrix. For example, if the coded matrixincludes rows 1, 2, and 4, the encoding matrix is reduced to rows 1, 2,and 4, and then inverted to produce the decoding matrix.

In a large DSN memory, memory devices are not always failing, but entireDS units may be failing when critical components break down within them.When the population of DS units is sufficiently large, and the time toreplace/repair failed DS units is known, then the number of requiredstand-by DS units becomes predictable. For example, in a population of10,000 DS units where 10 DS units fail each day, and it takes 2 days toreplace failed DS units, then on average there would be 20 failed DSunits at any time. In one embodiment, to reduce the requirement forrebuilding data, an equal population of stand-by DS units may beprovisioned, such that there are 10,020 total DS units, 20 of whichserve as spares. Whenever it is determined that a DS unit has failed,one DS unit from the set of standby DS units is selected, and assignedthe encoded data slice namespace (DSN addresses) ranges previously heldby the failed DS unit. The replacement DS unit is then removed from theset of standby DS units. All writes to that range will then go to thisstand-by DS unit during the period the other DS unit remains failed.Most reads to this replacement DS unit fail (unless they are reads forrecently written data). Upon such time that the failed DS unit isrestored, the namespace range is set back to the recovered DS unit, andthe replacement DS unit begins migrating all data written to it to thisrestored DS unit. Once it has completed migrating all its data to therestored DS unit, it returns to the set of stand-by DS units.

FIG. 9 is a schematic block diagram of another embodiment of a dispersedstorage network (DSN) that includes the distributed storage and task(DST) processing unit 16 (computing device) of FIG. 1, the network 24 ofFIG. 1, an active DST execution (EX) unit pool 530 and a standby DSTexecution unit pool 532. The DST processing unit 16 includes the DSTclient module 34 of FIG. 1. Each of the active and standby DST executionunit pools 530-532 includes a set of DST execution units. For example,the active DST execution unit pool 530 includes DST execution units A1through AM and the standby DST execution unit pool 532 includes DSTexecution units S1 through SN, where the active DST execution unit pool530 includes M DST execution units and the standby DST execution unitpool 532 includes N DST execution units. Each DST execution unit may beimplemented utilizing the DST execution unit 36 (Storage Units (SU)) ofFIG. 1.

The DSN functions to utilize storage resources for accessing data storedin at least one of the active DST execution unit pool 530 and thestandby DST execution unit pool 532. In an example of operation of theutilizing of the storage resources, the DST client module 34 determinesa failure rate of DST execution units of the active DST execution unitpool 530. The determining includes tracking how many DST execution unitsfail per day, identifying a mean time to repair, and calculating a rateof failed units per day=failing units per day multiplied by days torepair.

Having determined the failure rate, the DST client module 34 establishesa number of standby DST execution units of the standby DST executionunit pool 532 based on the determined failure rate of the DST executionunits of the active DST execution unit pool. The establishing includesone or more of issuing an alert, commissioning a dormant DST executionunit, enabling a disabled DST execution unit, or repurposing anavailable standby DST execution unit.

When detecting a failed DST execution unit of the active DST executionunit pool, the DST client module 34 identifies an associated DSN addressrange of the failed DST execution unit. The identifying includes atleast one of receiving the DSN address range, initiating a query,interpreting a query response, or performing a lookup. Having identifiedthe associated DSN address range, the DST client module 34 selects anavailable standby DST execution unit. The selecting may be based on oneor more of an availability level, a storage capacity level, around-robin selection scheme, or utilization of a distributed agreementprotocol function (e.g., a highest ranked DST execution unit isselected).

Having selected the standby DST execution unit, the DST client module 34facilitates populating the selected standby DST execution unit with oneor more encoded data slices associated with the failed DST executionunit based on the associated DSN address range. The facilitatingincludes at least one of rebuilding encoded data slices of theassociated DSN address range, storing rebuilt encoded data slices in thestandby DST execution unit, and updating slice location information(e.g., of a DSN directory, of an index) to associate the DSN addressrange with the selected standby DST execution unit and to disassociatethe DSN address range with the failed DST execution unit.

Having facilitated the populating of the selected standby DST executionunit, the DST client module 34 facilitates processing of the receiveddata access requests 534 for data associated with the DSN address rangeby utilizing the selected standby DST execution unit. For example, theDST client module 34 communicates standby slice access messages 540 withthe standby DST execution unit.

When detecting availability of the failed DST execution unit, the DSTclient module 34 facilitates reactivating the now available andpreviously failed DST execution unit. For example, the DST client module34 transfers (e.g., via standby slice access messages 540) the rebuiltencoded data slices from the selected standby DST execution unit to thenow available DST execution unit (e.g., via active slice access messages538), associates the DSN address range with the now available DSTexecution unit, and disassociates the DSN address range with theselected standby DST execution unit.

Having reactivated the now available and previously failed DST executionunit, the DST client module 34 facilitates processing of further receivedata access requests 534 for the data associated with the DSN addressrange by utilizing the now available DST execution unit. For example,the DST client module 34 communicates slice access requests 536 asactive slice access messages with the now available DST execution unit,and receives slice access responses 542.

FIG. 9A is a flowchart illustrating an example of utilizing storageresources. The method includes step 550 where a processing module (e.g.,of a distributed storage and task (DST) client module) determines afailure rate of storage units of an active storage unit pool. Thedetermining includes identifying unit failures per day and mean time torepair (rate of failed units per day=failing units per day multiplied bydays to repair). The method continues at step 552 where the processingmodule establishes a number of standby storage units. That is, theprocessing module activates a number of standby storage units inaccordance with the failure rate. For example, in a population of 10,000DS units where 10 DS units fail each day, and it takes 2 days to replacefailed DS units, then on average there would be 20 failed DS units atany time. In one embodiment, to reduce the requirement for rebuildingdata, an equal population of stand-by DS units may be provisioned, suchthat there are 10,020 total DS units, 20 of which serve as spares.

When detecting a failed storage unit of the active storage unit pool,the method continues at step 554 where the processing module identifiesan associated DSN address range. The identifying includes at least oneof performing a lookup, interpreting an error message, or interpreting aquery response. The method continues at step 556 where the processingmodule selects an available standby storage unit. The selecting may bebased on one or more of an availability level, a storage capacity level,a list, or a distributed agreement protocol function output.

The method continues at step 558 where the processing module facilitatespopulating (encoded data slice migration) the selected standby storageunit with one or more encoded data slices associated with the failedstorage unit based on the associated DSN address range. For example, theprocessing module rebuilds the encoded data slices of the DSN addressrange associated with the failed storage unit, stores the rebuiltencoded data slices in the standby storage unit, associates the DSNaddress range with the standby storage unit, and disassociates the DSNaddress range with the failed storage unit.

The method continues at step 560 where the processing module facilitatesprocessing the received data access requests for data associated withthe DSN address range by utilizing the selected standby storage unit.For example, the processing module attempts to recover encoded dataslices of the DSN address range from the standby storage unit.

When detecting activation of a replacement storage unit for the failedstorage unit, the method continues at step 562 where the processingmodule facilitates populating the replacement storage unit with one ormore encoded data slices from the selected standby storage unit, wherethe one or more encoded data slices are associated with the DSN addressrange. The replacement storage unit may include the failed storage unitwhen the failed storage unit has been repaired. In an example of thefacilitating, the processing module transfers all encoded data slices ofthe DSN address range from the standby storage unit to the replacementstorage unit.

The method continues at step 564 where the processing module facilitatesprocessing of further receive data access requests for data associatedwith the DSN address range by utilizing the replacement storage unit.For example, the processing module attempts to recover encoded dataslices of the DSN address range from the replacement storage unit.

The method described above in conjunction with the processing module canalternatively be performed by other modules of the dispersed storagenetwork or by other computing devices. In addition, at least one memorysection (e.g., a non-transitory computer readable storage medium) thatstores operational instructions can, when executed by one or moreprocessing modules of one or more computing devices of the dispersedstorage network (DSN), cause the one or more computing devices toperform any or all of the method steps described above.

It is noted that terminologies as may be used herein such as bit stream,stream, signal sequence, etc. (or their equivalents) have been usedinterchangeably to describe digital information whose contentcorresponds to any of a number of desired types (e.g., data, video,speech, audio, etc. any of which may generally be referred to as‘data’).

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “configured to”, “operably coupled to”, “coupled to”, and/or“coupling” includes direct coupling between items and/or indirectcoupling between items via an intervening item (e.g., an item includes,but is not limited to, a component, an element, a circuit, and/or amodule) where, for an example of indirect coupling, the intervening itemdoes not modify the information of a signal but may adjust its currentlevel, voltage level, and/or power level. As may further be used herein,inferred coupling (i.e., where one element is coupled to another elementby inference) includes direct and indirect coupling between two items inthe same manner as “coupled to”. As may even further be used herein, theterm “configured to”, “operable to”, “coupled to”, or “operably coupledto” indicates that an item includes one or more of power connections,input(s), output(s), etc., to perform, when activated, one or more itscorresponding functions and may further include inferred coupling to oneor more other items. As may still further be used herein, the term“associated with”, includes direct and/or indirect coupling of separateitems and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that acomparison between two or more items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signal1 has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1. As maybe used herein, the term “compares unfavorably”, indicates that acomparison between two or more items, signals, etc., fails to providethe desired relationship.

As may also be used herein, the terms “processing module”, “processingcircuit”, “processor”, and/or “processing unit” may be a singleprocessing device or a plurality of processing devices. Such aprocessing device may be a microprocessor, micro-controller, digitalsignal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on hard coding of thecircuitry and/or operational instructions. The processing module,module, processing circuit, and/or processing unit may be, or furtherinclude, memory and/or an integrated memory element, which may be asingle memory device, a plurality of memory devices, and/or embeddedcircuitry of another processing module, module, processing circuit,and/or processing unit. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module,module, processing circuit, and/or processing unit includes more thanone processing device, the processing devices may be centrally located(e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that if the processing module, module, processing circuit,and/or processing unit implements one or more of its functions via astate machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory and/or memory element storing the correspondingoperational instructions may be embedded within, or external to, thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry. Still further note that, the memoryelement may store, and the processing module, module, processingcircuit, and/or processing unit executes, hard coded and/or operationalinstructions corresponding to at least some of the steps and/orfunctions illustrated in one or more of the Figures. Such a memorydevice or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claims. Further, the boundariesof these functional building blocks have been arbitrarily defined forconvenience of description. Alternate boundaries could be defined aslong as the certain significant functions are appropriately performed.Similarly, flow diagram blocks may also have been arbitrarily definedherein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence couldhave been defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claims. One of average skill in the art will alsorecognize that the functional building blocks, and other illustrativeblocks, modules and components herein, can be implemented as illustratedor by discrete components, application specific integrated circuits,processors executing appropriate software and the like or anycombination thereof.

In addition, a flow diagram may include a “start” and/or “continue”indication. The “start” and “continue” indications reflect that thesteps presented can optionally be incorporated in or otherwise used inconjunction with other routines. In this context, “start” indicates thebeginning of the first step presented and may be preceded by otheractivities not specifically shown. Further, the “continue” indicationreflects that the steps presented may be performed multiple times and/ormay be succeeded by other activities not specifically shown. Further,while a flow diagram indicates a particular ordering of steps, otherorderings are likewise possible provided that the principles ofcausality are maintained.

The one or more embodiments are used herein to illustrate one or moreaspects, one or more features, one or more concepts, and/or one or moreexamples. A physical embodiment of an apparatus, an article ofmanufacture, a machine, and/or of a process may include one or more ofthe aspects, features, concepts, examples, etc. described with referenceto one or more of the embodiments discussed herein. Further, from figureto figure, the embodiments may incorporate the same or similarly namedfunctions, steps, modules, etc. that may use the same or differentreference numbers and, as such, the functions, steps, modules, etc. maybe the same or similar functions, steps, modules, etc. or differentones.

Unless specifically stated to the contra, signals to, from, and/orbetween elements in a figure of any of the figures presented herein maybe analog or digital, continuous time or discrete time, and single-endedor differential. For instance, if a signal path is shown as asingle-ended path, it also represents a differential signal path.Similarly, if a signal path is shown as a differential path, it alsorepresents a single-ended signal path. While one or more particulararchitectures are described herein, other architectures can likewise beimplemented that use one or more data buses not expressly shown, directconnectivity between elements, and/or indirect coupling between otherelements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of theembodiments. A module implements one or more functions via a device suchas a processor or other processing device or other hardware that mayinclude or operate in association with a memory that stores operationalinstructions. A module may operate independently and/or in conjunctionwith software and/or firmware. As also used herein, a module may containone or more sub-modules, each of which may be one or more modules.

As may further be used herein, a computer readable memory includes oneor more memory elements. A memory element may be a separate memorydevice, multiple memory devices, or a set of memory locations within amemory device. Such a memory device may be a read-only memory, randomaccess memory, volatile memory, non-volatile memory, static memory,dynamic memory, flash memory, cache memory, and/or any device thatstores digital information. The memory device may be in a form a solidstate memory, a hard drive memory, cloud memory, thumb drive, servermemory, computing device memory, and/or other physical medium forstoring digital information.

While particular combinations of various functions and features of theone or more embodiments have been expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent disclosure is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

What is claimed is:
 1. A method for execution by one or more processingmodules of one or more computing devices of a dispersed storage network(DSN), the method comprises: determining a failure rate of storage unitsof an active storage unit pool; establishing a number of standby storageunits based on the determined failure rate; identifying, upon detectinga failed storage unit of the active storage unit pool, an associated DSNaddress range of the failed storage unit; selecting an available standbystorage unit; facilitating populating the selected available standbystorage unit with one or more encoded data slices associated with thefailed storage unit based on the associated DSN address range;facilitating processing received data access requests for dataassociated with the associated DSN address range by utilizing theselected available standby storage unit; facilitating, upon detectingactivation of a replacement storage unit for the failed storage unit,population of the replacement storage unit with the one or more encodeddata slices from the selected available standby storage unit, where theone or more encoded data slices are associated with the associated DSNaddress range; and facilitating processing of further receive dataaccess requests for data associated with the associated DSN addressrange by utilizing the replacement storage unit.
 2. The method of claim1, wherein the determining a failure rate of storage units of an activestorage unit pool includes identifying a number of the failed storageunits per day and mean time to repair each of the failed storage units.3. The method of claim 1, wherein the determining a failure rate ofstorage units of an active storage unit pool includes tracking how manystorage units fail per day, identifying a mean time to repair, andcalculating a rate of failed units per day=failing units per daymultiplied by days to repair.
 4. The method of claim 1, wherein theestablishing a number of standby storage units includes activating anumber of standby storage units in accordance with the determinedfailure rate.
 5. The method of claim 1, wherein the identifying includesat least one of performing a lookup, interpreting an error message, orinterpreting a query response.
 6. The method of claim 1, wherein theselecting may be based on one or more of: an availability level, astorage capacity level, a list, or a distributed agreement protocolfunction output.
 7. The method of claim 1, wherein the facilitatingpopulating the selected available standby storage unit includesrebuilding the encoded data slices of the associated DSN address rangeassociated with the failed storage unit, storing the rebuilt encodeddata slices in the selected available standby storage unit, associatingthe associated DSN address range with the selected available standbystorage unit, and disassociating the associated DSN address range withthe failed storage unit.
 8. The method of claim 1, wherein the utilizingthe selected available standby storage unit includes the processingmodule attempting to recover encoded data slices of the associated DSNaddress range from the selected available standby storage unit.
 9. Themethod of claim 1, wherein the replacement storage unit includes thefailed storage unit when the failed storage unit has been repaired. 10.The method of claim 1, wherein the facilitating, upon detectingactivation of a replacement storage unit for the failed storage unit,population of the replacement storage unit includes transferring allencoded data slices of the associated DSN address range from theselected standby available storage unit to the replacement storage unit.11. The method of claim 1, wherein facilitating processing of furtherreceive data access requests includes attempting to recover encoded dataslices of the associated DSN address range from the replacement storageunit.
 12. A computing device of a group of computing devices of adispersed storage network (DSN), the computing device comprises: aninterface; a local memory; and a processing module operably coupled tothe interface and the local memory, wherein the processing modulefunctions to: determine a failure rate of storage units of an activestorage unit pool; establish a number of standby storage units based onthe determined failure rate; identify, upon detecting a failed storageunit of the active storage unit pool, an associated DSN address range ofthe failed storage unit; select an available standby storage unit;facilitate populating the selected available standby storage unit withone or more encoded data slices associated with the failed storage unitbased on the associated DSN address range; facilitate processingreceived data access requests for data associated with the associatedDSN address range by utilizing the selected available standby storageunit; facilitate, upon detecting activation of a replacement storageunit for the failed storage unit, population of the replacement storageunit with the one or more encoded data slices from the selectedavailable standby storage unit, where the one or more encoded dataslices are associated with the associated DSN address range; andfacilitate processing of further receive data access requests for dataassociated with the associated DSN address range by utilizing thereplacement storage unit.
 13. The computing device of claim 12, whereinthe determine a failure rate of storage units of an active storage unitpool includes identifying a number of the failed storage units per dayand mean time to repair each of the failed storage units.
 14. Thecomputing device of claim 12, wherein the determine a failure rate ofstorage units of an active storage unit pool includes tracking how manystorage units fail per day, identifying a mean time to repair, andcalculating a rate of failed units per day=failing units per daymultiplied by days to repair.
 15. The computing device of claim 12,wherein the establish a number of standby storage units includesactivating a number of standby storage units in accordance with thedetermined failure rate.
 16. The computing device of claim 12, whereinthe facilitate populating the selected available standby storage unitincludes rebuilding the encoded data slices of the associated DSNaddress range associated with the failed storage unit, storing therebuilt encoded data slices in the selected available standby storageunit, associating the associated DSN address range with the selectedavailable standby storage unit, and disassociating the associated DSNaddress range with the failed storage unit.
 17. The computing device ofclaim 12, wherein the utilize the selected available standby storageunit includes the processing module attempting to recover encoded dataslices of the associated DSN address range from the selected availablestandby storage unit.
 18. The computing device of claim 12, wherein thereplacement storage unit includes the failed storage unit when thefailed storage unit has been repaired.
 19. A system comprises: aninterface; a local memory; and a processing module operably coupled tothe interface and the local memory, wherein the processing modulefunctions to: determine a failure rate of storage units of an activestorage unit pool; establish a number of standby storage units based onthe determined failure rate; identify, upon detecting a failed storageunit of the active storage unit pool, an associated DSN address range ofthe failed storage unit; select an available standby storage unit;facilitate populating the selected available standby storage unit withone or more encoded data slices associated with the failed storage unitbased on the associated DSN address range; facilitate processingreceived data access requests for data associated with the associatedDSN address range by utilizing the selected available standby storageunit; facilitate, upon detecting activation of a replacement storageunit for the failed storage unit, population of the replacement storageunit with the one or more encoded data slices from the selectedavailable standby storage unit, where the one or more encoded dataslices are associated with the associated DSN address range; andfacilitate processing of further receive data access requests for dataassociated with the associated DSN address range by utilizing thereplacement storage unit.
 20. The system of claim 19, wherein thedetermine a failure rate of storage units of an active storage unit poolincludes tracking how many storage units fail per day, identifying amean time to repair, and calculating a rate of failed units perday=failing units per day multiplied by days to repair.